Black Copper Maran or Jersey Giant?

I recently bought 10 BCM and 10 JG chicks and they all came in a box together they all look the same and I can't tell them apart. The Marans are for my brother and now I don't know how to separate them to give him his half of chicks. Any and all help with infirmation on how to tell them apart would be so helpful!

Marans tend to have light feathering on the sides of their legs. As chicks, it may only appear as fuzz, and it may take a few days to start coming in. Jersey giant chicks are clean legged birds, so there should not be any leg feathering.